Maybe not ADD, clattering noise when trying to engage 4wd high or lo

I was having trouble engaging my 4wd this past weekend (bunch of chattering like the front diff was trying to engage). I took apart the front diff ADD and found that the small switch was bad, arcing and one small copper lead was broken). Put new ADD in and most of the chattering stopped, but not all (now does go into 4wd hi and lo). I checked the transfer case oil and it was grey (only 30,000 since my last change, total of 60,000 on vehicle) with some metal flakes. The first time I changed the transfer oil at 30,000 it looked brand new. Filled with the 75w90 Valvoline LSD oil and now I'm back to almost quiet. The chattering is mostly gone, but still noticeable clunks and clatter occasionally when in 4wd that were not there before.
Could this be a bad breather on the transfer case/transmission letting water into the transfer case? I spray water on my wheel wells and engine bay occasionally to clean out leaves and dirt. I am wondering if the water I spray got into the transfer case breather.

 

update: 4wd will now not engage at all. took Tacoma with just over 61,000 miles to the dealer. The transfer case actuator went as well and damaged parts inside the transfer case. $2,750 for new actuator and to rebuild the transfer case. $3,700 for new transfer case and new actuator both by the dealer. Very disappointed with the quality of the original parts. I've followed all fluid changes and maintenance schedules. How can Toyota produce a mechanical part that can cause that much damage to the transfer case in just over 60,000 miles. I'll be looking at other models when I trade this in.

 

Consider a private shop. I was quoted 8000$ for new transmission on my 07 with 150k, replaced elsewhere for 1500$

 

update: transfer case actuator failed and caused damage to the transfer case internal parts. Replaced both with new parts. Frustrating because I have just over 61,000 mile. I bought the Toyota new in 2010 and have followed all maintenance. Took the dealer two weeks to diagnose and get all parts in. I have my Tacoma back, but not sure how much longer I will keep it.

 

I have never heard of this happening. Sounds like tough luck.